The human skeleton is composed of 206 individual bones that perform a variety of important functions, including support, movement, protection, storage of minerals, and formation of blood cells. These bones can be grouped into two categories, the axial skeleton and the appendicular skeleton. The axial skeleton consists of 80 bones that make up the body's center of gravity, and the appendicular skeleton consists of 126 bones that make up the body's appendages. The axial skeleton includes the skull, vertebral column, ribs, and sternum, among others, and the appendicular skeleton includes the long bones of the upper and lower limbs, and the clavicles and other bones that attach these long bones to the axial skeleton, among others.
To ensure that the skeleton retains its ability to perform its important functions, and to reduce pain and disfigurement, fractured bones should be repaired promptly and properly. Typically, fractured bones are treated using fixation devices that reinforce the fractured bones and keep them aligned during healing. Fixation devices may take a variety of forms, including casts and external fixators for external fixation, and bone plates, wires, and/or threaded fasteners (e.g., bone screws) for internal fixation.
Bone plates are implants that may be positioned under skin and other soft tissue for mounting on the bone adjacent the fracture. These plates may be manufactured and/or custom bent for mounting to particular regions of bone. To use a bone plate to repair a fractured bone, a surgeon (1) selects an appropriate plate, (2) reduces (sets) the fracture, and (3) fastens the plate to the bone on opposing sides of the fracture using suitable fasteners, such as bone screws, so that the bone plate spans the fracture and fragments of the bone are substantially fixed in position.
A potential disadvantage to the use of bone plates is the amount of tissue damage produced by installation. For example, to access a target site on bone, a bone plate may be placed onto the bone through an incision in soft tissue that overlaps much of the target site and is comparable in size to the length of the bone plate. Alternatively, to reduce the amount of injury to soft tissue, the bone plate may be inserted through an incision that is shorter than the bone plate. In this case, the bone plate only partially overlaps the incision and extends away from the incision under soft tissue. However, the bone plate may be difficult to advance under soft tissue to achieve this partial overlap with the incision.
To facilitate advancement under soft tissue, bone plates may be manufactured with a beveled end. However, for practical reasons, the beveled end generally is too rigid and blunt to be effective. First, the flexibility of the beveled end may be limited by the composition of the bone plate, which is typically metal. Second, if the beveled end were to be fabricated as very thin, such a thin beveled end would create a segment of the bone plate that is not rigid enough to be effective for bone fixation, thereby reducing the effective length of the bone plate. Third, if the beveled end were to be fabricated as relatively sharp to facilitate separation of soft tissue and bone, the sharp beveled end may produce tissue irritation over time as tissue rubs against the end of the bone plate after its installation. Accordingly, other approaches to installing bone plates under soft tissue are needed.